GOVERNMENT ENGINNERING COLLAGE,VALSAD

11

IRRIGATION ENGINEERING(170602)

GUIDED BY:-Prof. Kuldip Patel

PREPARED BY

NAME ENROLLMENT NO.

PATEL NIRALI A. 100190106003

KHOLIYA ASHISH B. 110193106011

Irrigation engineering

Necessity of irrigation

Scope of irrigation engineering

Benefits of irrigation engineering

Ill-effect of irrigation

Irrigation development in india

Types of irrigation system

Soil-water plant relationship

Classification of soil water

Soil-moisture content

Depth of soil water available to plants

IRRIGATION:-Irrigation is defined as the process of artificially

supplying water to soil for raising crops.

IRRIGATION ENGINEERING:- It is the science dealing

with planning, designing, construction, operation and maintenance

of various irrigation works

Inadequate rainfall

Non-uniform rainfall

Growing number of crops during year

Growing perennial crops

Growing superior crops

Increasing the yield of crops

Insurance against crops

Engineering aspect

Agriculture aspect

Management aspect

It involves the development of source of water for irrigation

and arrangement for the conveyance of water from the source

right up to agricultural fields.

a) Storage ,diversion or lifting of water.

b) Conveyance of water to the agricultural fields.

c) Application of water to agricultural fields.

d) Drainage and reliving water – logging.

e) Development of hydropower.

It involves the timely and systematic application of irrigation

water to the agricultural fields. It deals with following points:

1) Proper leveling and shaping of the agricultural fields.

2) Soil investigation and classification of the agriculural land.

3) Provision of field channel.

4) Distribution of water uniformly and periodically.

5) Capacities of different soil.

6) Conservation of soil against erosion.

7) Choosing proper crop pattern.

8) Reclamation of waste and alkaline ands.

It deals with the successful implementation and efficient management of both the engineering as well as the agricultural aspects of the project.

Following points are considered in this aspect:-

1) The farmers should be trained and educated.

2) The cultivation should be carried out in a scientific manner with due control on all the inputs so as to obtain the maximum yield.

3) The distribution of water to the farmers should be managed properly.

4) The agricultural land holding of the small farmers should be consolidated to increase the efficiency of irrigation.

5) Suitable measures are to be adopted to eliminate the ill effect of irrigation.

1) Increase in crop yield

2) Protection from famine

3) Cultivation of crash crops

4) Elimination of mixed cropping

5) Increase in the wealth of country

6) Increase in prosperity of people

7) Generation of hydro-electric power

8) Domestic and industrial water suplly

9) Inland navigation

10) Communication facility

11) Canal plantation

12) Increase in ground water storage

13) Overall development of the country

14) Aid in civilization

It is due to the excess irrigation and unscientific use of

irrigation water may give rise to the ill-effects. some of the

common ill-effect of irrigation are:

1) Water logging

2) Mosquitoes nuisance

3) Damp climate

4) Pollution of ground water

Classification based on availability of waterIrrigation

system

Flow

irrigationLift

irrigation

Perennial

irrigation

As per

sourceInundation

irrigationWell

irrigation

Lift canal

irrigation

Direct

irrigation

Storage

irrigation

Combined

irrigation

The flow irrigation system can be further classified based on duration into two classes:

1) Perennial irrigation system

2) Inundation irrigation system

PERENNIAL IRRIGATION SYSTEM:-

In this system water is supplied as per the crop requirements at regular intervals, through the crop period.

INUNDATION IRRIGATION SYSTEM:-

In this system large quantity of water flowing in a river during flood is allowed to flood or inundated the land to be cultivated.

Major project

(CCA >10,000)

Medium project

10,000<CCA>2000

Minor project

CCA<2000

(20 km²)

The water added to a soil mass during irrigation ,is held in the

pores of the soil mass, which is termed as soil water. It is

classified as following:-

1) Gravitational water

2) Capillary water

3) Hygroscopic water

SOIL MOISTURE CONTENTT:-The amount of water present in soil is

termed as soil moisture content.

SATURATION CAPACITY:-It is the amount of water required to fill all

the pore spaces between soil particles by replacing all air held in pore

spaces.

FIELD CAPACITY:-The field capacity is the moisture content of the soil

after free drainage has removed most of the gravity water.

PERMANENT WILTING POINT:-Permanent wilting point or the

wilting coefficient is that water content at which plants can no longer

extract sufficient water from the soil for its growth.

TEMPORARY WILTING:- Temporary Wilting of plants usually occurs

on a hot day, but the plants recover - from wilting in the cooler portion of

the day or during the night without any addition of water to the soil. Thus,

temporary wilting of plants may occur even without much reduction in the

soil moisture content.

ULTIMATE WILTING:-Ultimate wilting of plants Occurs when they

become completely wilted and dead after ultimate wilting has occurred, the

plants do not recover from wilting even after the addition of water to the

soil.

The water content at which ultimate wilting occurs is termed

as ultimate wilting point.

MOISTURE EUIVALENT:- Moisture equivalent is Defined as the

percentage of moisture retained in an initially saturated sample of soil 10

mm thick after being subjected to a centrifugal force of 1000 times gravity

for a period of 30 minutes.

AVAILABLE MOISTURE:- The difference in Moisture content of soil

between the field capacity and the permanent wilting point is called the

available moisture.

READILY AVAILABLE MOISTURE :-It is that portion of the Available

moisture that is most easily extracted by plants. It is approximately 75% of

the available moisture.

SOIL MOISTURE TENSION:-The force per unit area that Must be

exerted in order to extract water from the soil is known as soil moisture

tension.

In irrigation, it is essential to know the amount of waterneeded by crops.

This determines the quantity of water to be added byirrigation and rainfall and helps in day to day managementof irrigation systems.

DUTY:-

Duty represents the irrigating capacity of a unit water. It relation

between the area of a crop irrigated and the quantity of irrigation water

required during crop growth.

For example:If 5 cumec of water is required for a crop sown in an area of 5000 hectares, The duty will be 5000/5=1000 hectares/cumec.

DELTA:-

It is total depth of water required for a crop during the entire

period the crop is in the field and is denoted by Δ. The unit of delta is days.

There are four types of duty:

1) GROSS DUTY:-It is the duty of water measured at The head of main

canal.

2) NOMINAL DUTY:-It is the duty sanctioned as per Schedule of an

irrigation department.

3) ECONOMIC WATER DUTY:-It is the duty of water Which results in

the maximum crop yield.

4) DESIGNATED DUTY:- It is the duty of water assumed in an irrigation

project for designing capacities of the channel.

Let,

D=duty in hectares

∆ = total depth of water supplied in meters

B = base period in days

1) If we take a field of area D hectares, water supplied to the field corresponding to the water depth ∆ meters will be,

= D x ∆ hectares – meters

=D x ∆ x 104 cubic meters

2) For the same field of area D hectares , water is supplied at the rate of 1 cumec for the entire base period of B days , then the total quantity of water supplied to the field,

=1 x b x 24 x 60 x 60 cubic meter

=8.64 x 104 B cubic meter

D = 8.64 B/ D meters

CROP PERIOD:-It is the time in days, that a crop takes from The instant

of its sowing to that of its harvesting.

BASE PERIOD:- The base period is the relation between he First

watering and the last watering supplied to the land.

PALEO:- It is defined as the first watering before sowing the Crop.

GROSS COMMAND AREA(G.C.A):-It is defined as the total Area lying

between drainage boundaries which can be commanded or irrigated by a

canal.

CUTURABLE COMMAND AREA(C.C.A):- It is that portion of G.C.A

which is cultivable or cultivable.

CROP RATIO:- It is defined as the ratio of the land irrigated During the

two main crop season rabi and kharif.

TIME FACTOR:- It is the ratio of number of days the canal has actually

run to the number of days of irrigation Period.

CAPACITY FACTOR:- It is the ratio of mean supply to the Full supply

of a canal.

1) Method of irrigation

2) System of irrigation

3) Method of cultivation

4) Type of crop

5) Base period of crop

6) Climatic condition

7) Quality of water

8) Canal condition

9) Type of soil and sub soil

10) Time of irrigation

Composed of two sub processes:-◦ Evaporation occurs on surfaces of open water or from vegetation and

ground surfaces.

◦ Transpiration is the removal of water from the soil by plant roots,

transported through the plant into the leaves and evaporated from the

leaf’s stomata.

Typically combined in mass balance equations because the components are

difficult to partition.

Evapotranspiration

EvaporationTranspiration

Open

Water Soil Vegetation

Surfaces

Plants

Potential ET (PET) is the amount of evaporation that will occur if an

unlimited amount of water is available.

Actual ET (AET) is the actual amount of evaporation that occurs when

water is limited. For large areas can use a mass balance approach to

calculate (Eq. 4.5).

Transpiration is the loss of water in the form of vapor from plants

Factors that affect transpiration rates

Type of plant

Wind

Plant Available Water: the portion of water in a soil that can readily be absorbed by plant roots. Amount of water released between field capacity (amount of water remaining in the soil after gravitation flow has stopped) and wilting point (amount of water in the soil at 15 bars of suction).

Phase change of water from a liquid to a gas

o Rate of evaporation is driven by the vapor pressure deficit. Function of:

1. The ability of air to hold water based on air temperature and relative

humidity.

1. The energy in the water largely based on temperature.

o Net evaporation ceases when the air has reached the saturation vapor

pressure.

There are two method for the measurement :

DIRECT MEASUREMENT METHOD

1. Tank and lysimeter method

2. Field experiment method

3. Soil moisture study

4. Integration method

5. Inflow and outflow studies

USE OF EMPIRICAL FORMULA

1. Penman method

2. Jensen –Haise method

3. Blanley Criddle method

4. Hargreaves method

5. Thornthwait method

ET R GK

BP

e e

rn

z z

a

0

10

1622

( )[(

*)( ) (

*)(. )

( )]

•More reliable for any length period daily, monthly, or seasonal.

•If adequate data available.

AET0 = The evapotranspiration for grass

reference crop

= heat of vaporization

Rn = net radiation

G = soil heat flux

= slope of the vapor pressure curve

= psychrometric constant

= density of air

BP = mean barometric pressure

e0

z = average saturated vapor pressure

ez = actual vapor pressure

* = (1+rc/ra)

rc = surface resistance to vapor transport

ra = aerodynamic resistance to sensible heat and

vapor transport

K1 = the dimension coefficient

These irrigation efficiencies are brought about by the desire not to wasteirrigation water, no matter how cheap or abundant it is.

The objective of irrigation efficiency concept is to determine whetherimprovements can be made in both the irrigation system and themanagement of the operation programmes, which will lead to an efficientirrigation water use.

APPLICATION EFFICIENCY

EWater in root zone after irrigation

Total volume of water applieda

Total vol of water applied Vol of Tailwater Vol of deep percolation

Total water applied

. ( . . )

Ea is inadequate in describing the overall quantity of water since it does not

indicate the actual uniformity of irrigation, the amount of deep percolation or

the magnitude of under-irrigation. See diagrams in text.

Water Conveyance Efficiency

EWater delivered to the Farm W

Water of water diverted from a stream reservoir or well Wc

d

s

( )

, ( )

Farm

Water lost by evapAnd seepage

Wd

Ws

EVolume of water in the root zone after irrigation

Volume of water needed in root zone to avoid total water moisture depletions

=WS/WN X 100

Irrigation projects are planned, executed, owned, and operated by state

governments. Irrigation projects are financed by state governments out of

their own resources, market borrowing and loans and grants made available

by the central governments. the beneficiaries in commanded areas derive

considerable benefits from the project. It is , therefore, imperative that the

beneficiaries pay for it. The fixation of such charges is known as

assessment of irrigation water.

1) Assessment on area basis or crop rate basis

2) Volumetric assessment

3) Assessment on seasonal basis

4) Composite rate basis

5) Permanent assessment